This invention relates to an endoscope having an insertion section adapted to be inserted into a body cavity of a human subject, and a control section for controlling the insertion section from outside of the body cavity.
In general, the insertion section of an endoscope has an illumination optical system for allowing light from a light source to be emitted toward the inner wall of a body cavity of a human subject, and a distal end portion having an objective optical system for receiving the light which has been reflected from the inner wall. An optical system located at the distal end portion of the endoscope generally comprises a plurality of lenses with spaces defined between adjacent pairs. After the insertion section of the conventional endoscope has been inserted into the body cavity of the human subject, there is the possibility that water vapor present in the gap between adjacent lenses may condense on the surface of each lens, leading to an accumulation of moisture thereon. In practice, the greater the amount of water vapor in the gap, the more liable is the lens to cloud over. When the lens of the optical system becomes clouded over, it is then difficult, if not impossible, to clearly observe a region of interest of the humane subject.
One conceivable method for preventing condensation of water vapor on the lens surface, is for a drying step to be performed in the gap between the lenses. Another method would be for the lens temperature to be kept higher than the ambient temperature. In practice, however, either of these methods is combersome and complicated to carry out.